The Alchemy Of Ratings: What TV Show Dies Next

Wondering whether your favorite show is going to be the next to face the axe in a season that's seeing ratings fall and networks get nervous? It turns out that it's not as entirely random and malicious as you may have suspected (Although I'm still a little worried about Pushing Daisies' chances, to be honest); there may even be an art to predicting which shows have the most to worry about, according to some. But what is the "renew/cancel index," and does it really help us to know how close to death Knight Rider may be?